The field of the invention generally relates to vision aids for allowing persons with low vision to see by enhancing an image of interest, and more specifically to a portable vision aid which can capture an image, display a portion of a magnified (enlarged) version of the image, and pan around the magnified image in response to motion of the portable vision aid.
Various vision aids exist to provide improved viewing of subject matter within a field of view of the vision aid by magnifying (enlarging) the perceived field of view. Many such aids allow those with impaired vision to view printed materials (e.g., books and magazines), digital displays (e.g., LCD, LED, or other monitors), and photographs by creating magnified images of the material or images of the material which may also include enhanced color contrast and/or brightness. This may be useful for people with difficulty in reading, due to blurred vision, macular degeneration, or other vision impairments.
Existing viewing aids typically include a camera, and a viewing surface within a field of view of the camera. If the material remains at a fixed location on the viewing surface, then either the camera is moved relative to the viewing surface (and material), or the viewing surface (and material) is moved relative to the camera. If the material rests freely on the viewing surface, then the material itself may also be moved relative to the camera (and viewing surface). In either case, successive images of the material captured by the camera are either projected on a separate screen such as with CCTV systems, or on a display integrated with the camera.
For those viewing aids involving movement of the camera, the precision required to position the camera to capture images of the target portion(s) of the material may be difficult to achieve in many situations. This may be especially so if the material is printed material intended for reading, and even more so for those who have macular degeneration and need the image to be enlarged, and/or those with motor skill impairments and/or difficulty with hand-eye coordination. The same is true for those viewing aids involving movement of the viewing surface and/or material, as is done with X-Y tables.
A number of portable low vision devices have also been developed for general vision situations (i.e., not viewing reading material or subject matter on a viewing surface). These portable low vision devices typically utilize electronic video cameras which are mounted in a fixture, such as a helmet or goggle that can be worn on the user's head, or a handheld instrument fixture. The devices have a display for displaying a magnified image of the video captured by the video camera. The image of the field of view being displayed by such devices is changed by adjusting the field of view of the video camera to obtain video of a different field of view. This can make it very challenging to keep the video camera steady and/or trained at a particular field of view, and even more so when a user is trying to adjust the device, such as the level of magnification, while viewing and scanning the desired field of view. Hence, these types of devices can be awkward and difficult to use, especially for persons already having low vision.